Hot-wire arc additive manufacturing Ti–6.5Al–2Zr–1Mo–1V titanium alloy: Pore characterization, microstructural evolution, and mechanical properties

Hot-Wire Arc Additive Manufacturing (HWAAM) is a promising process to fabricate large-scale integral components. Systematic researches are necessary to establish the initial material-processing-microstructure-property relationships in HWAAM. In this study, two TA15 titanium alloy block parts were built by HWAAM with two batches of wire. Notches on the wire surface and wire warpage aggravated the porosity of the built part. Quantitative characterization and analysis of pores were performed by X-ray computed tomography. Most of the pores were clustered at the fusion boundary. The porosity of the bead body zone was higher than that of the bead overlap zone. The equivalent diameters of pores primarily concentrated in a narrow range of variation. Spherical trapped gas pores were induced by hydrogen rejection. Irregularly shaped lack of fusion pores were caused by arc length variation, wire warpage and excessive heat input. The formation of equiaxed β grains were promoted by high porosity and low temperature gradient in the bead body zone. The poor ductility of the part with high porosity was attributed to the presence of pores and grain boundary α, while relatively high tensile strength of the part was attributed to the solid solution strengthening and boundary strengthening.